Heretofore, the major purpose of air filtration was to reduce the density of dust, consisting mostly of 0.2 micron, or larger, particles from air. Recent environmental concerns in the living, industrial and military environs have expanded the desired scope of air filtration into the "suppression of odor and virus/germs." Yet current air purification methods are hindered in many ways by an inability to capture undesirable submicron particles, microorganisms, odors, and substances efficiently and economically without suffering from high pressure drop, short life, energy inefficiency, and poor reliability. Simply stated, there is no current adequate method to meet the needs of modern air purification.
There have been thousands of experiments, research efforts, and patents made in the field of air filtration. However, all of this work has followed three existing basic principles: (1) the mechanical filter (mechanical blocking of airborne particles by mesh) (a few hundred years old--but still the most common and widely used method); (2) the electrostatic precipitator (invented 90 years ago in 1906 by Cottrelle, which relies on ionization and the Coulomb's law attraction of particle separation for filtration); and (3) the precharged synthetic fiber filter (precharged fibers create an electrostatic field within the filter material and interact with and capture airborne particles).
The present invention is directed to apparatus and method whereby a properly set non-ionizing electrical field creates a random, high speed, and churning motion of airborne particles in perpendicular directions to the air flow through a filter medium placed in the electric field, see U.S. Pat. No. 5,368,635.
This churning motion inside of a filter medium dramatically increases the probability of particles to bombard the surfaces of the fibers which compose the filter medium. Thus, a combination of such motion and Van der Waals force interaction between particles and fiber surfaces tremendously increases the probability of capturing particles throughout the filter material. This method efficiently captures a wide range of particles, in fact, even submicron particles which are much, much smaller than the porosity of the filter medium used.
The present invention is basically directed to apparatus for positioning of electrodes and a porous material in order to electrify by inducts one of the electrodes with a voltage which results in increase trapping of particular suspended in a gaseous fluid stream. This in turn dramatically upgrades the efficiency of filtration of most of the filter media known today, including paper, glass fiber, synthetic fiber, cloth, natural fiber, foam and electrostatically charged materials. This apparatus and method provides the advantages of 1) high efficiency of filtration, 2) capturing particles in a wide range of sizes, including below submicron sizes, 3) the least amount of pressure drop, 4) improvement in energy efficiency, and 5) low cost. These advantages are achieved without any change in the mechanical properties of the filter.